To date, the clinical assessment of joint pathologies, primarily those involving soft tissues or other ligment injuries, is subjective in nature. The clinician primarily relies on the manual manipulation of the joint. During clinical examination, the clinician obtains a subjective "feel" for the amount of laxity or stiffness that is present in the involved joint as compared to the clinician's previous experience regarding what the normal joint stiffness should feel like and/or as compared with the intact contralateral joint. This clinical examination is then supplemented by the patient clinical history and by radiological evaluations. Moreover, the assessment of the effectiveness of treatment, be it cast therapy, surgery, etc., is completely subjective and relies to a great extent on feedback from the patient. Consequently, there is a need for a quantitative, reliable technique to assess the flexibility of a joint for the purposes of contributing to the clinical management of joint pathologies.
Aside from the need for a more objective assessment of joint pathologies, there is also a need for providing an objective analysis in the design and evaluation of footwear. That is, there is a need to determine the level of support (three dimensional load-displacement and flexibility characteristics) provided to a joint such as the ankle joint by athletic footwear and to evaluate the quality of fit of this footwear. Currently, athletic shoes and other foot and ankle supporting devices are designed purely on an intuitive basis. There is no objective means for determining the quantitative support provided by a particular footwear design to provide the designer with sufficient feedback to rationally modify the design of the footwear for better performance.
In addition to the need for objective clinical assessment of joint pathology, there is also a need for improved post-operative and post trauma treatment of patient's joints. In the past, post-operative and post-trauma treatment of patient's joints commonly included immobilization. The affected joints were fixed by casts or traction for an extended duration. As a result of such immobilization, various medical problems commonly arose. In particular, capsular, ligamentous and articular adhesions, thromboembolism, yenos stasis, post-traumatic osteopenia, peripheral edema, muscle atrophy, and the like were commonly attributed to the immobilization.
It is now known that immobilization related medical problems could be reduced or eliminated by early immobilization of the effected joint. It has been found to be advantageous to initiate joint mobilization immediately following orthopedic surgery, in many instances in the operating and recovery rooms while the patient is still under anesthesia. Specifically, continuous passive motion of the effected joints has been found to be effective in reducing or eliminating the above-referenced medical problems, promoting faster healing, reducing the amount of pain in medications, improving the range of movement of the affected joint after recovery, and the like.
Continuous passive motion devices (CPMs) are typically motor driven and are designed to exercise a particular joint by repeatedly extending and flexing the joint. CPMs are capable of applying continuous motion to the joint in a repeatable, consistent manner and can be adjusted to operate at different speeds and within a defined range of motion. In such CPMs, it is important that the joint be anatomically aligned on the CPM. The limb is typically supported on a moveable carriage or frame member which is driven by the motor. The carriage or frame member includes a plate or other straps or padding (generally referred to as "soft goods") for directly receiving the human joint or limb. Straps or the like are used to secure a portion of the limb or joint to the plate or soft goods. For instance, in the case of a CPM for a leg, usually only the foot is strapped to the CPM while the remaining portion of the leg merely rests on the soft goods.
The problem with a CPM that does not receive the joint in an anatomically correct manner is that it does not maintain consistent axial alignment with the three pivot axes of the patient's joint through the entire range of motion of the joint. While CPMs which receive limbs in an anatomically correct manner along a single pivot axis are known, there is a need for a CPM which can remain anatomically aligned with the joint along all three pivot axes regardless of the applied loads and torques to the apparatus.
The present invention is directed to an apparatus and method which will allow a clinician and footwear designer to determine the load-displacement and flexibility characteristics of a joint and footwear, respectively. The present invention is directed to ascertaining the angular and linear displacement of the joint about and along its pivot axes produced in response to applied torques and forces about and along the axes. Accordingly, the present invention provides an objective quantitative, reliable technique to assess the load-displacement and flexibility characteristics of anatomical joints which greatly contributes to the clinical management of joint pathologies as well as to the design of footwear. The present invention is also directed to a CPM for a joint which is capable of achieving consistent anatomical alignment with all three pivot axes of a joint during treatment.